Intramolecular interactions in vinculin control α-actinin binding to the vinculin head

Using blot overlay techniques we have investigated the interaction of vinculin with alpha-actinin. We show that an alpha-actinin binding site is located in the 90 kDa vinculin head and confirm a vinculin binding site in the C-terminal rod of alpha-actinin, as recently reported by McGregor et al. [(1994) Biochem. J. 310, 225-233]. The isolated vinculin head binds much more strongly to alpha-actinin than intact vinculin. Using a proteolytic 81 kDa head fragment, we show that vinculin residues 1-107 are required for alpha-actinin binding. Antibodies directed against vinculin residues 808-850 inhibit the vinculin-alpha-actinin binding, suggesting that this sequence is directly involved in, or topographically related to, the alpha-actinin binding site.